Semiconductor integrated circuit device with reduced leakage current

ABSTRACT

The gate tunnel leakage current is increased in the up-to-date process, so that it is necessary to reduce the gate tunnel leakage current in the LSI which is driven by a battery for use in a cellular phone and which needs to be in a standby mode at a low leakage current. In a semiconductor integrated circuit device, the ground source electrode lines of logic and memory circuits are kept at a ground potential in an active mode, and are kept at a voltage higher than the ground potential in an unselected standby mode. The gate tunnel leakage current can be reduced without destroying data.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 12/078,992filed Apr. 9, 2008, which is a Continuation of application Ser. No.11/452,275 filed Jun. 14, 2006, which is a Continuation of applicationSer. No. 11/288,287 filed Nov. 29, 2005, which is a Continuation ofapplication Ser. No. 11/104,488 filed Apr. 13, 2005, which is aContinuation of application Ser. No. 10/158,903 filed on Jun. 3, 2002.Priority is claimed based on U.S. application Ser. No. 12/078,992 filedApr. 9, 2008, which claims the priority of application Ser. No.11/452,275 filed Jun. 14, 2006, which claims the priority of U.S.application Ser. No. 11/288,287 filed Nov. 29, 2005, which claims thepriority of U.S. application Ser. No. 11/104,488 filed Apr. 13, 2005,which claims the priority of U.S. application Ser. No. 10/158,903 filedon Jun. 3, 2002, which claims the priority of Japanese Application Nos.2001-168945 and 2002-017840, filed on Jun. 5, 2001 and Jan. 28, 2002,respectively, all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor integrated circuitdevice and manufacturing method of the device, particularly to a staticrandom access memory (SRAM), on-chip memory mounted on a system LSI,microprocessor, system LSI, and the like.

As a known technique for reducing a gate tunnel leakage current, U.S.Pat. No. 6,307,236 is known. In the known example, when the gate tunnelleakage current is large, a power is cut off with a switch MOS having athick gate oxide layer and small gate tunnel leakage current, andthereby the leakage current is reduced in a disclosed circuit. Moreover,as a technique for reducing a gate induced drain leakage (GIDL) current,JP-A-2000-357962 is known. In the known example, on the assumption thata MOS transistor has a relatively small threshold value, in order toreduce a subthreshold leakage current, a substrate electrode of a Pchannel type MOS transistor is first controlled to be not less than apower voltage, and the substrate electrode of an N channel type MOStransistor is controlled to be not more than a ground potential. As aresult, GIDL is actually generated. To solve the problem, a technique ofreducing the power voltage to reduce the GIDL current is disclosed.Moreover, in JP-A-9-135029, as a GIDL current countermeasure, atechnique of implanting phosphorus ions in a gate electrode andsource/drain region of an N channel MIS transistor is disclosed.

In recent years, with miniaturization of a process, the MOS transistorhas had a gate oxide layer thickness of 4 nm or less. However, when thethickness of the gate oxide layer is 4 nm or less, the gate tunnelleakage current increases. When an activating voltage is suppliedbetween gate and source electrodes, the gate tunnel leakage current is10⁻¹² A/μm² or more in a typical process.

In an LSI for use in a cellular phone, there is a demand for standby ina low leakage current. Particularly, in a SRAM, it is necessary toretain data with a button battery for one week or more. When the processbecomes worst and the oxide layer becomes thin, the gate tunnel leakagecurrent increases and it is disadvantageously impossible to retain thedata for one week or more. Moreover, an increase of the GIDL current asthe leakage current flowing to a substrate from a drain similarly raisesa problem. However, in the conventional known example (U.S. Pat. No.6,307,236) for reducing the gate tunnel leakage current, the power iscut off with the MOS, and therefore there is a problem that dataretained in a SRAM cell, register file, latch circuit, and the like aredestroyed. Moreover, in the conventional known example(JP-A-2000-357962) for reducing the GIDL current, when the MOStransistor having a relatively high threshold value, for example, of 0.7V is used, the subthreshold leakage current is not remarkable.Therefore, even when the substrate electrode of the N channel type MOStransistor is set to a potential not more than the ground potential andthe substrate electrode of the P channel type MOS transistor is set to apotential not less than the power voltage, an off leakage current is notreduced, and all the more a junction leak current disadvantageouslyincreases.

SUMMARY OF THE INVENTION

A summary of a typical invention in inventions disclosed in the presentapplication will briefly be described hereinafter.

According to an aspect of the present invention, there is disclosed asemiconductor integrated circuit device comprising: at least one logiccircuit including a first current path having at least one N channeltype MOS transistor and a second current path having at least one Pchannel type MOS transistor, wherein terminals of the current paths ofthe logic circuit are connected to each other; and when one current pathis in a conductive condition, the other current path is in a nonconductive condition. In the at least one logic circuit, the otherterminal of the first current path is connected via a source line, thesource line is connected to a switch circuit, and the switch circuitkeeps the source line at a ground potential, when the at least one logiccircuit is selected to operate, and keeps the source line at a voltagehigher than the ground potential, when the logic circuit is not selectedand is in a standby condition.

A substrate electrode of the N channel type MOS transistor is connectedto the ground potential or the source line.

In the standby condition, the voltage supplied between gate and sourceelectrodes of the MOS transistor in an ON-state is smaller than a powervoltage. Therefore, the gate tunnel leakage current can be reduced, andretained data of a latch or the like is not destroyed.

Moreover, in the MOS transistor whose subthreshold current is smallerthan GIDL, and whose threshold value is high, the voltage suppliedbetween the gate and drain electrodes in an OFF-state is smaller thanthe power voltage, GIDL is reduced and an off current is reduced.However, since the ground potential or a voltage higher than the groundpotential is supplied to the substrate electrode of the N channel typeMOS transistor and the power voltage is supplied to the substrateelectrode of the P channel type MOS transistor, a junction leak currentdoes not increase.

FIG. 13 shows a dependence of current Ids between the drain and sourceof the N channel type MOS transistor on a gate voltage, whose thresholdvoltage is relatively high as about 0.7 V and whose subthreshold currentis smaller than the GIDL current. The current Ids is shown in alogarithmic scale. A case in which a drain voltage is set to the powervoltage (1.5 V) and a case in which the drain voltage is set to apotential (1.0 V) lower than the power voltage according to the presentinvention are shown. The source electrode and substrate electrode areconnected to the ground potential, and the substrate potential is notbiased. Since a potential difference supplied between the gate and draindrops and the GIDL current is reduced in the OFF-state, the leakagecurrent can be reduced.

Moreover, according to the present invention, there is provided asemiconductor device comprising: an N channel type MOS transistor inwhich arsenic is used in a region to make a contact and phosphorus isused in an extension region, in a source/drain region. In thesemiconductor device having the SRAM, the N channel type MOS transistoris used as an N channel type MOS transistor in a memory cell of an SRAM,and the N channel type MOS transistor, in which arsenic is used both inthe region to make the contact and the extension region, is used as an Nchannel type MOS transistor of a peripheral circuit to control thememory cell.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a semiconductor device integrated circuitaccording to a first embodiment;

FIG. 2 shows an operating waveform of the semiconductor deviceintegrated circuit according to the first embodiment;

FIG. 3 is a circuit diagram of the semiconductor device integratedcircuit according to a second embodiment;

FIG. 4 shows the operating waveform of the semiconductor deviceintegrated circuit according to the second embodiment;

FIG. 5 is a circuit diagram of a semiconductor memory device accordingto a third embodiment;

FIG. 6 shows operating waveforms during standby and during readaccording to the third embodiment;

FIG. 7 shows the operating waveforms during standby and during writeaccording to the third embodiment;

FIG. 8 is a circuit diagram of the semiconductor integrated circuitaccording to a fourth embodiment;

FIG. 9 is a circuit diagram of the semiconductor integrated circuitaccording to a fifth embodiment;

FIG. 10 is a circuit diagram of the semiconductor integrated circuitaccording to a sixth embodiment;

FIG. 11 is a circuit diagram of the semiconductor integrated circuitaccording to a seventh embodiment;

FIG. 12 shows the operating waveform of the semiconductor integratedcircuit according to the seventh embodiment;

FIG. 13 shows a current reducing effect of a MOS transistor in thepresent system;

FIG. 14 shows a leakage current reducing effect according to the thirdembodiment;

FIG. 15 is a schematic circuit diagram of the semiconductor memorydevice according to the third embodiment;

FIG. 16 is a characteristic diagram of a voltage down converteraccording to the third embodiment;

FIGS. 17A-17C are main part sectional views of a semiconductor substrateshowing a manufacturing method of a semiconductor integrated circuit ofthe present invention;

FIGS. 18A-18C are main part sectional views of the semiconductorsubstrate showing the manufacturing method of the semiconductorintegrated circuit of the present invention;

FIGS. 19A-19C are main part sectional views of the semiconductorsubstrate showing the manufacturing method of the semiconductorintegrated circuit of the present invention;

FIG. 20 is a main part sectional view of the semiconductor substrateshowing the manufacturing method of the semiconductor integrated circuitof the present invention;

FIG. 21 is a main part sectional view of the semiconductor substrateshowing the manufacturing method of the semiconductor integrated circuitof the present invention; and

FIGS. 22A and 22B are characteristic diagrams in which the manufacturingmethod of the present invention is applied.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Several preferred examples of a semiconductor memory device according tothe present invention will be described hereinafter with reference tothe drawings.

First Embodiment

FIG. 1 is a circuit diagram showing one embodiment of a semiconductordevice according to the present invention. The present circuit shows apart of a semiconductor integrated circuit constituted of a P channeltype MOS transistor MP and N channel type MOS transistor MN. The circuitis formed on a semiconductor substrate such as single crystal siliconusing a semiconductor integrated circuit manufacturing technique inwhich an insulating layer for use in a gate of the MOS transistor has athickness of 4 nm or less, and a gate tunnel leakage current is 10⁻¹²A/μm² or more at a power voltage of 1.5 V.

FIG. 1 shows an inverter circuit INV and a latch circuit LATCH whichretains data, as a part of a semiconductor integrated circuit device.

An inverter circuit INV102 is constituted of a P channel type MOStransistor MP102 and N channel type MOS transistor MN102. A gateelectrode of the P channel type MOS transistor MP102 is connected to aninput signal I0, a drain electrode thereof is connected to a connectionnode N0, and a source electrode thereof is connected to a power voltageVDD. Moreover, the substrate electrode of the P channel type MOStransistor MP102 is connected to the power voltage VDD. The gateelectrode of the N channel type MOS transistor MN102 is connected to theinput signal I0, the drain electrode thereof is connected to theconnection node N0, and the source electrode thereof is connected to aground source electrode line VSSM. Moreover, the substrate electrode ofthe N channel type MOS transistor MN102 is connected to the groundsource electrode line VSSM or a ground potential VSS.

An inverter circuit INV103 is constituted of a P channel type MOStransistor MP103 and N channel type MOS transistor MN103. The gateelectrode of the P channel type MOS transistor MP103 is connected to theconnection node N0, the drain electrode thereof is connected to aconnection node N1, and the source electrode thereof is connected to thepower voltage VDD. Moreover, the substrate electrode of the P channeltype MOS transistor MP103 is connected to the power voltage DD. The gateelectrode of the N channel type MOS transistor MN103 is connected to theconnection node N0, the drain electrode thereof is connected to theconnection node N1, and the source electrode thereof is connected to theground source electrode line VSSM. Moreover, the substrate electrode ofthe N channel type MOS transistor MN103 is connected to the groundsource electrode line VSSM or the ground potential VSS.

An inverter circuit INV104 is constituted of a P channel type MOStransistor MP104 and N channel type MOS transistor MN104. The gateelectrode of the P channel type MOS transistor MP104 is connected to theconnection node N1, the drain electrode thereof is connected to anoutput node O0, and the source electrode thereof is connected to thepower voltage VDD. Moreover, the substrate electrode of the P channeltype MOS transistor MP104 is connected to the power voltage VDD. Thegate electrode of the N channel type MOS transistor MN104 is connectedto the connection node N1, the drain electrode thereof is connected tothe output node O0, and the source electrode thereof is connected to theground source electrode line VSSM. Moreover, the substrate electrode ofthe N channel type MOS transistor MN104 is connected to the groundsource electrode line VSSM or the ground potential VSS.

The latch circuit LATCH is constituted of a flip-flop constituted byconnecting an input and output of a CMOS inverter (constituted of Pchannel type MOS transistors (MP105, MP106), and N channel type MOStransistors (MN105, MN106)), and information is stored in storage nodesN2 and N3.

The gate electrode of the P channel type MOS transistor MP105 isconnected to the storage node N3, the drain electrode thereof isconnected to the storage node N2, and the source electrode thereof isconnected to the power voltage VDD. Moreover, the substrate electrode ofthe P channel type MOS transistor MP105 is connected to the powervoltage VDD.

The gate electrode of the P channel type MOS transistor MP106 isconnected to the storage node N2, the drain electrode thereof isconnected to the storage node N3, and the source electrode thereof isconnected to the power voltage VDD. Moreover, the substrate electrode ofthe P channel type MOS transistor MP106 is connected to the powervoltage VDD.

The gate electrode of the N channel type MOS transistor MN105 isconnected to the storage node N3, the drain electrode thereof isconnected to the storage node N2, and the source electrode thereof isconnected to the ground source electrode line VSSM. Moreover, thesubstrate electrode of the N channel type MOS transistor MN105 isconnected to the ground source electrode line VSSM or the groundpotential VSS.

The gate electrode of the N channel type MOS transistor MN106 isconnected to the storage node N2, the drain electrode thereof isconnected to the storage node N3, and the source electrode thereof isconnected to the ground source electrode line VSSM. Moreover, thesubstrate electrode of the N channel type MOS transistor MN106 isconnected to the ground source electrode line VSSM or the groundpotential VSS.

Moreover, the N channel type MOS transistor MN101 which connects theground source electrode line VSSM to the ground potential VSS, and an Nchannel type MOS transistor MN100 which connects the ground sourceelectrode line VSSM to the potential VSSS higher than the groundpotential, for example, 0.5 V are disposed.

An active mode and standby mode will next be described using anoperating waveform shown in FIG. 2.

Here, the power voltage VDD is set to 1.5 V, the ground potential VSS isset to 0 V, and the potential VSSS higher than the ground potential isset to 0.5 V. The voltage is changed by properties of the device, andthe like.

In the active mode, the N channel type MOS transistor MN101 is on, andVSSM corresponds to the ground potential VSS, for example, 0 V. Thepotential of I0, N1 and N3 is 1.5 V, and the potential of N0 and N2 is 0V. In this case, the P channel type MOS transistors (MP103 and MP106)and N channel type MOS transistors (MN102, MN104 and MN105) are on, andthe P channel type MOS transistors (MP102, MP104 and MP105) and Nchannel type MOS transistors (MN103 and MN106) are off.

A voltage of 1.5 V is supplied between the gate and source electrodes ofthe P channel type MOS transistor MP103, and thereby a gate tunnelleakage current flows from the source electrode to the gate electrode.The current flows to the ground potential VSS through the connectionnode N0 and the N channel type MOS transistor MN102 in the ON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN104 and the gatetunnel leakage current flows from the gate electrode to the sourceelectrode. The current flows from the power voltage VDD through theconnection node N1 and the P channel type MOS transistor MP103 in theON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP106, and thereby thegate tunnel leakage current flows to the gate electrode from the sourceelectrode. The current flows to the ground potential VSS through theconnection node N2, and the N channel type MOS transistor MN105 in theON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN105, and thereby thegate tunnel leakage current flows from the gate electrode to the sourceelectrode. The current flows from the power voltage VDD through theconnection node N2 and the P channel type MOS transistor MP106 in theON-state.

The gate tunnel leakage current flows via the above-described path inthe active mode.

On the other hand, in the standby mode, the N channel type MOStransistor MN100 is on, and VSSM corresponds to the potential VSSShigher than the ground potential, for example, 0.5 V. The potential ofI0, N1 and N3 is 1.5 V, and the potential of N0 and N2 is 0.5 V. In thiscase, the P channel type MOS transistors (MP103 and MP106) and N channeltype MOS transistors (MN102, MN104 and MN105) are on, and the P channeltype MOS transistors (MP102, MP104 and MP105) and N channel type MOStransistors (MN103 and MN106) are off.

A voltage of 1.0 V is supplied between the gate and source electrodes ofthe P channel type MOS transistor MP103, and thereby the gate tunnelleakage current is reduced by about one digit as compared with when thepotential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN104, and thereby thegate tunnel leakage current is reduced by about one digit as comparedwith when the potential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP106, and thereby thegate tunnel leakage current is reduced by about one digit as comparedwith when the potential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and thesource electrodes of the N channel type MOS transistor MN105, andthereby the gate tunnel leakage current is reduced by about one digit ascompared with when the potential difference of 1.5 V is supplied.

Since the voltage supplied between the gate and source drops asdescribed above, the gate tunnel leakage current decreases. On the otherhand, the retained data is not destroyed. Moreover, since the voltagesupplied between the gate and the drain in the OFF-state drops, the GIDLcurrent also decreases.

In the present embodiment, the inverter circuit and the latch circuithave been described, but similar effects are obtained even in othersemiconductor integrated circuits such as a NAND circuit and NORcircuit.

Second Embodiment

FIG. 3 is a circuit diagram showing one embodiment of the semiconductordevice according to the present invention. The present circuit shows apart of the semiconductor integrated circuit constituted of the Pchannel type MOS transistor MP and N channel type MOS transistor MN. Thecircuit is formed on the semiconductor substrate such as single crystalsilicon using the semiconductor integrated circuit manufacturingtechnique in which the insulating layer for use in the gate of the MOStransistor has a thickness of 4 nm or less, and the tunnel leakagecurrent is 10⁻¹² A/μm² or more at the power voltage of 1.5 V.

FIG. 3 shows the inverter circuit INV and the latch circuit LATCH whichretains data, as a part of the semiconductor integrated circuit device.

An inverter circuit INV112 is constituted of a P channel type MOStransistor MP112 and N channel type MOS transistor MN112. The gateelectrode of the P channel type MOS transistor MP112 is connected to aninput signal I1, the drain electrode thereof is connected to aconnection node N4, and the source electrode thereof is connected to apower source electrode line VDDM. Moreover, the substrate electrode ofthe P channel type MOS transistor MP112 is connected to the power sourceelectrode line VDDM or the power voltage VDD. The gate electrode of theN channel type MOS transistor MN112 is connected to the input signal I1,the drain electrode thereof is connected to the connection node N4, andthe source electrode thereof is connected to the ground potential VSS.Moreover, the substrate electrode of the N channel type MOS transistorMN112 is connected to the ground potential VSS.

An inverter circuit INV113 is constituted of a P channel type MOStransistor MP113 and N channel type MOS transistor MN113. The gateelectrode of the P channel type MOS transistor MP113 is connected to theconnection node N4, the drain electrode thereof is connected to aconnection node N5, and the source electrode thereof is connected to thepower source electrode line VDDM. Moreover, the substrate electrode ofthe P channel type MOS transistor MP113 is connected to the power sourceelectrode line VDDM or the power voltage VDD. The gate electrode of theN channel type MOS transistor MN113 is connected to the connection nodeN4, the drain electrode thereof is connected to the connection node N5,and the source electrode thereof is connected to the ground potentialVSS. Moreover, the substrate electrode of the N channel type MOStransistor MN114 is connected to the ground potential VSS.

An inverter circuit INV114 is constituted of a P channel type MOStransistor MP114 and N channel type MOS transistor MN114. The gateelectrode of the P channel type MOS transistor MP114 is connected to theconnection node N5, the drain electrode thereof is connected to anoutput signal O1, and the source electrode thereof is connected to thepower source electrode line VDDM. Moreover, the substrate electrode ofthe P channel type MOS transistor MP114 is connected to the power sourceelectrode line VDDM or the power voltage VDD. The gate electrode of theN channel type MOS transistor MN114 is connected to the connection nodeN5, the drain electrode thereof is connected to the output signal O1,and the source electrode thereof is connected to the ground potentialVSS. Moreover, the substrate electrode of the N channel type MOStransistor MN114 is connected to the ground potential VSS.

The latch circuit LATCH is constituted of the flip-flop constituted byconnecting the input and output of the CMOS inverter (constituted of Pchannel type MOS transistors (MP115 and MP116) and N channel type MOStransistors (MN115 and MN116)), and the information is stored in storagenodes N6 and N7.

The gate electrode of the P channel type MOS transistor MP115 isconnected to the storage node N7, the drain electrode thereof isconnected to the storage node N6, and the source electrode thereof isconnected to the power source electrode line VDDM. Moreover, thesubstrate electrode of the P channel type MOS transistor MP115 isconnected to the power source electrode line VDDM or the power voltageVDD.

The gate electrode of the P channel type MOS transistor MP116 isconnected to the storage node N6, the drain electrode thereof isconnected to the storage node N7, and the source electrode thereof isconnected to the power source electrode line VDDM. Moreover, thesubstrate electrode of the P channel type MOS transistor MP116 isconnected to the power source electrode line VDDM or the power voltageVDD.

The gate electrode of the N channel type MOS transistor MN115 isconnected to the storage node N7, the drain electrode thereof isconnected to the storage node N6, and the source electrode thereof isconnected to the ground potential VSS. Moreover, the substrate electrodeof the N channel type MOS transistor MN115 is connected to the groundpotential VSS.

The gate electrode of the N channel type MOS transistor MN116 isconnected to the storage node N6, the drain electrode thereof isconnected to the storage node N7, and the source electrode thereof isconnected to the ground potential VSS. Moreover, the substrate electrodeof the N channel type MOS transistor MN116 is connected to the groundpotential VSS.

Moreover, a P channel type MOS transistor MP101 which connects theground source electrode line VDDM to the ground potential VDD, and a Pchannel type MOS transistor MP100 which connects a ground sourceelectrode line VDDM to a potential VDDD higher than the power voltage,for example, 1.0 V are disposed.

The active and standby modes will next be described using an operatingwaveform shown in FIG. 4.

Here, the power voltage VDD is set to 1.5 V, ground potential VSS is setto 0 V, and potential VDDD lower than the power voltage is set to 1.0 V.The voltage is changed by properties of the device, and the like.

In the active mode, the N channel type MOS transistor MN100 is on, andVDDM corresponds to the power voltage VDD, for example, 1.5 V. Thepotential of N4 and N7 is 1.5 V, and the potential of I1, N5 and N6 is 0V. In this case, the P channel type MOS transistors (MP112, MP114 andMP116) and N channel type MOS transistors (MN113 and MN115) are on, andthe P channel type MOS transistors (MP113 and MP115) and N channel typeMOS transistors (MN112, MN114 and MN116) are off.

A voltage of 1.5 V is supplied between the gate and source electrodes ofthe N channel type MOS transistor MN113, and thereby the gate tunnelleakage current flows from the gate electrode to the source electrode.The current flows from the power voltage VDD through the connection nodeN4 and the P channel type MOS transistor MP112 in the ON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP114, and thereby thegate tunnel leakage current flows from the source electrode to the gateelectrode. The current flows to the ground potential VSS through theconnection node N5 and the N channel type MOS transistor MN113 in theON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP116, and thereby thegate tunnel leakage current flows from the source electrode to the gateelectrode. The current flows to the ground potential VSS through theconnection node N6 and the N channel type MOS transistor MN115 in theON-state.

Similarly, a voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN115, and thereby thegate tunnel leakage current flows from the gate electrode to the sourceelectrode. The current flows from the power voltage VDD through theconnection node N6 and the P channel type MOS transistor MP116 in theON-state.

The gate tunnel leakage current flows via the above-described path inthe active mode.

On the other hand, in the standby mode, the P channel type MOStransistor MP101 is on, and VDDM corresponds to a potential VVDD lowerthan the power voltage, for example, 1.0 V. The potential of N4 and N7is 1.0 V, and the potential of I1, N5 and N6 is 0 V. In this case, the Pchannel type MOS transistors (MP112, MP114 and MP116) and N channel typeMOS transistors (MN113 and MN115) are on, and the P channel type MOStransistors (MP113 and MP115) and N channel type MOS transistors (MN112,MN114 and MN116) are off.

A voltage of 1.0 V is supplied between the gate and source electrodes ofthe N channel type MOS transistor MN113, and thereby the gate tunnelleakage current is reduced by about one digit as compared with when thepotential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP114, and thereby thegate tunnel leakage current is reduced by about one digit as comparedwith when the potential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP116, and thereby thegate tunnel leakage current is reduced by about one digit as comparedwith when the potential difference of 1.5 V is supplied.

Similarly, a voltage of 1.0 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN115, and thereby thegate tunnel leakage current is reduced by about one digit as comparedwith when the potential difference of 1.5 V is supplied.

Since the voltage supplied between the gate and the source drops asdescribed above, the gate tunnel leakage current decreases. On the otherhand, the retained data is not destroyed. Moreover, since the voltagesupplied between the gate and the drain drops in the OFF-state, the GIDLcurrent also decreases.

In the present embodiment, the inverter circuit and the latch circuithave been described, but similar effects are obtained even in the othersemiconductor integrated circuit such as an NAND circuit or an NORcircuit.

Third Embodiment

FIG. 5 is a circuit diagram showing one embodiment in which the presentinvention is applied to an SRAM. In a semiconductor manufacturingapparatus 98, the circuit constituted of the P channel type MOStransistor and N channel type MOS transistor is formed on thesemiconductor substrate such as single crystal silicon using thesemiconductor integrated circuit manufacturing technique in which theinsulating layer for use in the gate of the MOS transistor has athickness of 4 nm or less and the tunnel leakage current is 10⁻¹² A/μm²or more at the power voltage of 1.5 V.

The SRAM 98 as the semiconductor device is divided in a plurality ofmats MEMBLK. Details of the mats are shown in FIG. 5. A mat unit is, forexample, 2M bits, and the SRAM of 16 M is divided into eight mats. Avoltage down converter PWR generates inner power supplies (VDD, VSSS andVDDD) based on a power voltage VCC supplied from an outer pad todistribute the supplies to the respective mats. Data 116 from an inputbuffer INBUF turns to a decode signal and a control signal through apredecoder 115 and a control circuit 117, and the signals aredistributed to the respective mats. Each mat 108 is constituted of aplurality of base units 106. Each base unit is constituted of twocolumns of memory cells CELL.

A memory cell CELL0 is constituted of a flip-flop constituted byconnecting the input and output of a pair of CMOS inverters (constitutedof load P channel type MOS transistors (MO00 and MP01) and driver Nchannel type MOS transistors (MN00 and MN01)), and transfer N channeltype MOS transistors (MN02 and MN03) which selectively connect storagenodes NL0 and NR0 of the flip-flop to data lines (DT0 and DB0). The gateelectrodes of the N channel type MOS transistors (MN02 and MN03) areconnected to a subword line SWL0.

A memory cell CELL1 is constituted of a flip-flop constituted byconnecting the input and output of a pair of CMOS inverters (constitutedof P channel type MOS transistors (MP10 and MP11) and N channel type MOStransistors (MN10 and MN11)), and N channel type MOS transistors (MN12and MN13) which selectively connect storage nodes NL1 and NR1 of theflip-flop to data lines (DT1 and DB1). The gate electrodes of the Nchannel type MOS transistors (MN12 and MN13) are connected to thesubword line SWL0.

Moreover, the base unit includes a sense amplifier circuit (103), a readdata drive circuit (104), a write amplifier circuit (105), anequalizer/precharge circuits (99 and 100), and a Y switch circuits (101and 102). The sense amplifier circuit (103) is constituted of aflip-flop constituted of P channel type MOS transistors (MP20 and MP21)and N channel type MOS transistors (MN20 and MN21), a latch senseamplifier circuit constituted of an N channel type MOS transistor MN22which activates the sense amplifier, and switch circuits (MP22 andMP23). The gate electrodes of the MOS transistors (MN22, MP22 and MP23)are connected to an activating signal SA.

The Y switch circuit 101 includes P channel type MOS transistors (MP05and MP06) and N channel type MOS transistors (MN04 and MN05) whichconnect the data lines (DT0 and DB0) to the sense amplifier circuit 103.

The Y switch circuit 102 includes P channel type MOS transistors (MP15and MP16) and N channel type MOS transistors (MN14 and MN15) whichconnect the data lines (DT1 and DB1) to the sense amplifier circuit 103.

Control signals (YSW and YSWB) are signals for selecting whether thesense amplifier circuit 103 is connected to the data lines (DT0 and DB0)or the data lines (DT1 and DB1).

The write amplifier circuit 105 is constituted of two clocked inverters(CINV2 and CINV3) and an inverter INV0. A signal of a data bus 111 ispropagated to the data lines by control signals (WBC and WBCB).

The read data drive circuit 104 is constituted of two clocked inverters(CINV2 and CINV3). Read data is propagated to the data bus 111 bycontrol signals (RBC and RBCB).

The equalizer/precharge circuit 99 includes a P channel type MOStransistor MP02 which connects the power voltage VDD to the data lineDT0, a P channel type MOS transistor MP03 which connects the powervoltage VDD to the data line DB0, and a P channel type MOS transistorMP04 which connects the data line DT0 to the data line DB0. The gateelectrodes of the P channel type MOS transistors (MP02, MP03 and MP04)are connected to a control signal EQ.

The equalizer/precharge circuit 100 includes a P channel type MOStransistor MP12 which connects the power voltage VDD to the data lineDT1, a P channel type MOS transistor MP13 which connects the powervoltage VDD to the data line DB1, and a P channel type MOS transistorMP14 which connects the data line DT1 to the data line DB1. The gateelectrodes of the P channel type MOS transistors (MP12, MP13 and MP14)are connected to the control signal EQ.

Switch circuits (109 and 110) for supplying a voltage lower than thepower voltage, for example, 1.0 V to the data lines (DT and DB) in thestandby mode are disposed in the respective columns.

The switch circuit 109 is constituted of a P channel type MOS transistorMP07 for connecting a voltage VDDD lower than the power voltage to thedata line DT0, and a P channel type MOS transistor MP08 for connectingthe voltage VDDD lower than the power voltage to the data line DB0. Thegate electrodes of the P channel type MOS transistors (MP07 and MP08)are connected to a control signal CVDDD.

The switch circuit 110 is constituted of a P channel type MOS transistorMP17 for connecting the voltage VDDD lower than the power voltage to thedata line DT1, and a P channel type MOS transistor MP18 for connectingthe voltage VDDD lower than the power voltage to the data line DB1. Thegate electrodes of the P channel type MOS transistors (MP17 and MP18)are connected to the control signal CVDDD.

All memory cell ground source electrode lines VSSM in the memory mat 108are connected by a metal layer, and connected to the power supply by Nchannel type MOS transistors (MN6 and MN7). The N channel type MOStransistor MN6 is a transistor which connects the power supply VSSS forsupplying a voltage higher than the ground potential VSS to the groundsource electrode line VSSM, and the gate electrode thereof is connectedto a control signal STVSSM. The N channel type MOS transistor MN7 is atransistor which connects the ground potential VSS to the ground sourceelectrode line VSSM, and the gate electrode thereof is connected to acontrol signal ACVSSM.

The control signal STVSSM is generated by an AND circuit AND0 and aninverter circuit INV1 using a chip selecting signal CS and a matselecting signal MAT.

The control signal ACVSSM is generated by the AND circuit AND0 using thechip selecting signal CS and the mat selecting signal MAT.

The control signal CVDDD is generated by the AND circuit AND0 using thechip selecting signal CS and the mat selecting signal MAT.

Inputted address and control signal 116 are predecoded by the predecoder115, and the subword line SWL is generated by a word decoder/driver 114.

The control signal EQ is generated by a NAND circuit NAND0 using thechip selecting signal CS, the mat selecting signal MAT, and the resetpulse ATD.

The control signals (YSWB and YSW) are generated by an inverter circuitINV2 using a Y address AY.

The control signal SA is generated by an AND circuit AND2 and invertercircuits (INV3 and INV4) using the chip selecting signal CS, the matselecting signal MAT, and the write selecting signals WE and FSEN. FSENis a timing pulse generated by ATD.

The control signals (RBC and RBCB) are generated by an inverter circuitINV5 using the control signal SA.

The control signals (WBC and WBCB) are generated by an AND circuit AND3and an inverter circuit INV6 using the chip selecting signal CS, the matselecting signal MAT, and the write selecting signal WE.

The control signals (CS, WE, YA, MAT and ATD) are generated from theinputted address and control signal using a control circuit 117. For themat selecting signal MAT, as shown in FIG. 15, another control circuit118 is sometimes used to prepare a fast mat selecting signal FMAT. Theword line is selected in full consideration of a processdispersion/timing in order to prevent a misoperation. However, forcircuits driven to read/write with respect to the memory cells (acircuit for controlling an operating potential in a selecting condition,an equalizer/precharge circuit, and the like), as long as the circuitsoperates faster than the selection of the word line, a control precisionof the timing may be dropped. Then, a MOSFET (including either the Pchannel type or the N channel type) having a high threshold value isused in the control circuit 117 for selecting the word line. The MOSFET(including either the P channel type or the N channel type) having twotypes of threshold values including high and low threshold values isused in the control circuit 118 which outputs a signal for activatingthe circuit driven to read/write the information with respect to thememory cell. When the MOSFET having the low threshold value is included,the circuit is weakened with respect to the process dispersion, and itis difficult to obtain the precision of an output timing. However, thecontrol circuit 118 can output the mat selecting signal faster than thecontrol circuit 117. The same circuit constitution may be used tosimplify design. The MOSFET having a threshold value lower than that ofthe control circuit for controlling the selection of the word line isincluded, and the types of threshold values are increased, so that acircuit for controlling the circuit driven to read/write the informationwith respect to the memory cell is constituted. Thereby, the precisionof the timing of the mat selecting signal MAT for selecting the wordline is raised. Additionally, the output timing of the mat selectingsignal FMAT for selecting the circuit driven to read/write theinformation with respect to the memory cell can securely be set to beearlier than the mat selecting signal MAT. This constitution iseffective particularly in designing a memory device which is of anasynchronous type and whose precision of the selecting timing is strict.The fast mat selecting signal FMAT is used, instead of the mat selectingsignal MAT, in the AND circuit AND0 of a circuit for controlling thememory cell ground source electrode line VSSM, the AND circuit AND1 of acircuit for controlling the VDDD supply, and the NAND circuit NAND0 of acircuit for controlling the equalizer/precharge.

A read operation performed from the standby mode will next be describedwith reference to the operating waveform shown in FIG. 6. When the chipselecting signal CS is in “L” (“LOW” level) or the mat is not selected,the memory mat is in the standby mode. In this case, the voltage VSSShigher than the ground potential, for example, 0.5 V is supplied to thememory cell ground source electrode line VSSM. Moreover, the voltageVDDD lower than the power voltage VDD, for example, 1.0 V is supplied tothe data lines (DT and DB). In this case, the storage node NL0 of thememory cell CELL0 indicates 0.5 V, and NR0 indicates the power voltageVDD, for example, 1.5 V. A voltage of 1.0 V lower than the power voltageof 1.5 V is supplied between the gate and source electrodes of the Pchannel type MOS transistor MP01 in the ON-state, and thereby the gatetunnel leakage current is reduced. Moreover, a voltage of 1.0 V lowerthan the power voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN00 in the ON-state,and thereby the gate tunnel leakage current is reduced. Furthermore, avoltage of 1.0 V lower than the power voltage of 1.5 V is suppliedbetween the gate and source electrodes of the transfer N channel typeMOS transistors (MN02 and MN03) in the OFF-state, and thereby the GIDLcurrent is reduced.

When the chip selecting signal CS turns to “H” or the address changes,the ATD pulse is generated and the read operation is started. The memorycell ground source electrode line VSSM of the selected mat 108 is set tothe ground potential 0 V by the mat selecting signal MAT and the chipselecting signal CS. Moreover, the P channel type MOS transistors (MP07,MP08, MP17 and MP18) having supplied the voltage VDDD to the data lines(DT and DB) turn off.

The data lines (DT and DB) are precharged to obtain the power voltageVDD by the control signal EQ generated from the ATD pulse.

As a result, the storage node NL0 of the memory cell CELL0 indicates 0V, and NR0 indicates the power voltage VDD, for example, 1.5 V. Thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP01 in the ON-state,and thereby the gate tunnel leakage current increases. Moreover, thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN00 in the ON-state,and thereby the gate tunnel leakage current increases. Furthermore, thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the transfer N channel type MOS transistors (MN02 andMN03) in the OFF-state, and thereby the GIDL current increases.

Thereafter, the word line SWL0 is selected, a micro potential differenceis generated in the data lines (DT and DB), the sense amplifier circuit103 is activated by the control signal SA, thereby the micro potentialdifference is amplified, and the data is outputted to the data bus 111.

A write operation performed from the standby mode will next be describedwith reference to the operating waveform shown in FIG. 7. The standbymode is similar to the read operation.

When the chip selecting signal CS turns to “H” or the address changes,the ATD pulse is generated and the write operation is started. Thememory cell ground source electrode line VSSM of the selected mat 108 isset to the ground potential 0 V by the mat selecting signal MAT and thechip selecting signal CS. Moreover, the P channel type MOS transistors(MP07, MP08, MP17 and MP18) having supplied the voltage VDDD to the datalines (DT and DB) turn off.

The data lines (DT and DB) are precharged by the control signal EQgenerated from the ATD pulse to obtain the power voltage VDD.

As a result, the storage node NL0 of the memory cell CELL0 indicates 0V, and NR0 indicates the power voltage VDD, for example, 1.5 V. Thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the P channel type MOS transistor MP01 in the ON-state,and thereby the gate tunnel leakage current increases. Moreover, thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the N channel type MOS transistor MN00 in the ON-state,and thereby the gate tunnel leakage current increases. Furthermore, thepower voltage of 1.5 V is supplied between the gate and sourceelectrodes of the transfer N channel type MOS transistors (MN02 andMN03) in the OFF-state, and thereby the GIDL current increases.

Thereafter, the word line SWL0 is selected. The signal of the data bus111 is inputted into the data lines (DT and DB), and the data is writtenin the memory cell CELL by this signal.

In the present embodiment, the source voltage of the memory cell israised to 0.5 V in the standby mode, but the power supply of the memorycell may be lowered to 1.0 V. Additionally, when the standby modechanges to the active mode, this transition is requested to be performedat a high speed as compared with when the active mode changes to thestandby mode. Therefore, when the source voltage is raised to 0.5 V inthe standby mode, a burden on a power supply circuit is reduced ascompared with when the power supply of the memory cell is lowered to 1.0V. Therefore, it is more advantageous to raise the source voltage to 0.5V. Moreover, as seen from characteristics of FIG. 13, even with the same0.5 V, to raise the source voltage on a low potential side can be saidto be advantageous in lowering the current.

FIG. 14 shows leakage currents of one SRAM cell in the standby andactive modes. The GIDL current, the subthreshold leakage current, andGIDL are all reduced in the standby mode. FIG. 16 shows one example ofcharacteristics of the voltage down converter PWR. When the potentialsVDDD to be supplied to a bit line, and the like, and the operatingpotentials (high potential VDD and low potential VSSS) to be supplied tothe memory cells are generated, and when the potential VCC supplied fromthe outer pad indicates a value not less than a predetermined value, thepotential supplied from the outer pad is controlled and outputted inthis constitution. For example, when the potential supplied from theouter pad is 1.5 V or less, the high potential VDD supplied to thememory cell is the same as the power voltage VCC supplied from the outerpad. When VCC is 1.5 V or more, VDD is controlled to be constant at 1.5V. Moreover, for the potential VDDD lower than the power voltage, theVCC of 1.0 V or less is the same as the potential VCC supplied from theouter pad, and the VCC of 1.0 V or more is controlled to be constant at1.0 V. The potential VSSS higher than the ground potential is 0 V, whenthe VCC is 1.0 V or less. When the potential VCC supplied from the outerpad is 1.0 V or more, the potential is controlled based on the potentialVDD on the high potential side supplied to the memory cell so as to be avalue lower by 1.0 V. Thereby, when the power voltage VCC inputted fromthe outside of the semiconductor chip fluctuates, the voltage suppliedto the memory cell is constantly 1.0 V and the data can be preventedfrom being destroyed. Additionally, since the potential VSS on the lowpotential side supplied from another outer pad is the ground potential,the potential can be considered not to fluctuate. The application of theoperating potential generation circuit which can be controlled by afeedback circuit is not limited to the semiconductor integrated circuitincluding the memory, and is also effective in the above-describedembodiment.

In the present embodiment, to reduce the GIDL current, the semiconductordevice includes the N channel type MOS transistor in which arsenic isused in a region to make a contact, and phosphorus is used in anextension region in a source/drain region. In the semiconductor deviceincluding the SRAM, the above-described N channel type MOS transistor isused in the N channel type MOS transistor in the memory cell of theSRAM, and the N channel type MOS transistor in which arsenic is usedboth in the region to make the contact and the extension region is usedin the N channel type MOS transistor of a peripheral circuit to controlthe memory cell.

In FIG. 22, arsenic is used in the regions to make the contact in thesource/drain regions of the N channel type MOS transistor. When arsenicis used in the extension region, a gate voltage Vgs and characteristicsIds of the current between the source and drain are shown in FIG. 22A.When phosphorus is used in the extension region, the gate voltage Vgsand characteristics Ids of the current between the source and drain areshown in FIG. 22B. Coordinates are the same in FIGS. 22A and 22B. Asapparent from the waveforms, an off leakage current in the gate voltageof 0.0 V apparently drops in FIG. 22B where phosphorus is used.Furthermore, in the system of the present invention (the system in whichan operating potential Vssm of the memory cell is raised from 0.0 V to0.5 V in the standby mode), when phosphorus is used in the extensionregion, the off leakage current can effectively be reduced. It is seenthat the effect in a high-temperature operating region is remarkable,although this is not shown here. Since phosphorus (P) more largelyfluctuates in device characteristics such as Vth-lowering characteristicthan arsenic (As), and a current driving force drops as compared withAs, it is difficult to adjust an ion implantation concentration or anenergy. Therefore, in general, arsenic has been used in the region tomake the contact and the extension region. In JP-A-1997-135029, a devicestructure is disclosed in which phosphorus is used both in the region tomake the contact and the extension region. However, the present inventoret al, has disclosed that the implanting of phosphorus in the extensionregion is effective for reducing the GIDL current, and the using ofarsenic in the region to make the contact is effective from capabilities(current driving force, short channel characteristic) of the device.These effects are obtained because a band bend by a vertical electricfield from the gate electrode is alleviated by implanting phosphorus inthe extension region overlapping under the gate electrode. Moreover,when an implantation profile is broadened, a junction electric fieldstrength of the vertical direction of channel and extension regions isalleviated, and an effect of reduction of PN junction leak alsocontributes to this.

FIGS. 17 to 21 are sectional views showing one example of amanufacturing method of the semiconductor device according to thepresent embodiment in order of steps. The respective views show an Nchannel type MOS transistor Qmn and P channel type MOS transistor Qmpconstituting a memory cell area MC, an N channel type MOS transistor Qpnand P channel type MOS transistor Qpp constituting a peripheral circuitarea PERI, and an N channel type MOS transistor Qhn and P channel typeMOS transistor Qhp constituting a high voltage inflicted area HV in adivided manner. The N channel type MOS transistor Qmn constituting thememory cell area MC is used in the driver and transfer MOS transistorsof each memory cell CELL of FIG. 5. The P channel type MOS transistorQmp constituting the memory cell area MC is used in the load MOStransistor of each memory cell CELL of FIG. 5. The N channel type MOStransistor Qpn and P channel type MOS transistor Qpp constituting theperipheral circuit area PERI are used in the P and N channel type MOStransistors other than those of the memory cell area of FIG. 5. That is,the MOS transistors for use in the sense amplifier circuit (103), readdata drive circuit (104), write amplifier circuit (105),equalizer/precharge circuits (99 and 100) and Y switch circuits (101 and102), word decoder/driver (114), predecoder (115), and control circuit(117) are included. The N channel type MOS transistor Qhn and P channeltype MOS transistor Qhp constituting the high voltage inflicted area HVare used in the N and P channel type MOS transistors constituting thecircuits having different operating voltages of input and output, thatis, the input buffer (INBUF), voltage down converter (PWR), andinput/output circuit IO of FIG. 15.

The method will be described hereinafter in order of the steps withreference to the drawings. First, as shown in FIG. 17A, a semiconductorsubstrate 200 formed of p type single crystal silicon is prepared, andan isolating region 201 is formed in the main surface of thesemiconductor substrate 200. The isolating region 201 can be formed, forexample, as follows. First, a silicon oxide layer (SiO₂) and siliconnitride layer (Si₃N₄) are successively formed on the main surface of thesemiconductor substrate 200, a patterned photo resist is used to etchthe silicon nitride layer, and the etched silicon nitride layer is usedas a mask to form a trench type isolating region in the semiconductorsubstrate 200. Thereafter, an insulating layer to fill in the trenchtype isolating region, such as the silicon oxide layer, is deposited, aCMP process or the like is used to remove the silicon oxide layer of theregion other than the trench type isolating region, and further a wetetching process or the like is used to remove the silicon nitride layer.Thereby, the isolating region (trench isolation) 201 is formed. Theisolating region is not limited to the trench type isolating region, andmay also be formed of a field insulator, for example, by a localoxidation of silicon (LOCOS) process. To alleviate a damage of thesurface of the semiconductor substrate by the subsequent ion implantingstep, a thin silicon oxide layer is deposited.

Thereafter, the patterned photo resist is used as the mask toion-implant an impurity, and p type wells 210 and 212 and n type wells211 and 213 are formed as shown in FIG. 17B. Impurities indicating a pconductivity type such as boron B and boron fluoride BF2 areion-implanted in the p type wells, and impurities indicating an nconductivity type such as phosphorus P and arsenic As are ion-implantedin the n type wells. Thereafter, impurities (the impurity (P) indicatingthe n conductivity type in the N channel type MOS transistor, and theimpurity (BF2) indicating the p conductivity type in the P channel typeMOS transistor) for controlling the threshold value of the MOSFET areion-implanted in the respective well regions.

Subsequently, as shown in FIG. 17C, a silicon oxide layer 221 forming agate insulating layer is formed. In this case, photolithography andetching techniques were used to form a thick gate oxide layer in thehigh voltage inflicted area, and a thin gate oxide layer in theperipheral circuit area and the memory cell area. In the presentembodiment, the film thickness of the thick gate oxide layer was set to8.0 nm in order to handle an external input/output of 3.3 V, and thethickness of the thin gate oxide layer was set to 3.0 nm, at which thegate leakage current raises a problem in the standby mode. After theoxide layer other than the layer of the high voltage inflicted area isremoved using the photolithography/wet etching technique, the layer isthermally oxidized and the oxide films having two types of filmthickness are formed. Thereafter, a poly crystal silicon layer 222 forthe gate electrode is deposited, and resist masks 223 are used toion-implant the n/p type impurities (phosphorus and boron) in theelectrode regions of the N and P channel type MOS transistors.

As shown in FIG. 18A, the photolithography/dry etching is used toprocess, and thereby form gate electrodes 230, 231, 232, 233, 234 and235. Subsequently, as shown in FIG. 18B, a semiconductor region formingthe extension region, and a semiconductor region for suppressing a punchthrough, having the conductivity type opposite to the type of theextension region (the same conductivity type as that of a well, andconcentration higher than that of a well region), are formed by an ionimplanting process. In the N channel type MOS transistor, masks (steps)are changed with the memory cell area MC, the peripheral circuit areaPERI and the high voltage inflicted area HV to perform the ionimplantation. In the memory cell area MC, to reduce the GIDL current inthe standby mode, phosphorus as the n type impurity and boron as the ptype impurity are implanted to form n type semiconductor regions 241 and242 and p type semiconductor regions 243 and 244. In this case, theother regions (P channel type MOS transistor region, and the peripheralcircuit region/high voltage inflicted region) are masked with theresist. In the peripheral circuit area PERI, phosphorus as the n typeimpurity and boron as the p type impurity are implanted to form n typesemiconductor regions 241 and 242 and p type semiconductor regions 243and 244 in order to realize the high-speed operation. In this case, theother regions (P channel type MOS transistor region, and the memory cellregion/high voltage inflicted region) are masked with the resist.Subsequently, as shown in FIG. 18C, the p type impurity (boron) and then type impurity (As) are implanted in the n type well 211 forming the Pchannel type MOS transistor, and thereby semiconductor regions 251, 254,255 and 256 forming the extension region, and semiconductor regions 253,254, 257 and 258 for suppressing the punch through, which are of thesame conductivity type as that of the well and has a concentrationhigher than the well region, are formed. In the P channel type MOStransistor, since the type and condition (energy) of the ionimplantation of the peripheral circuit area PERI are not changed, thesame mask (step) is used. When the ion is implanted, the region formingthe N channel type MOS transistor and the region forming the P channeltype MOS transistor of the high voltage inflicted area HV are maskedwith the resist. When arsenic and phosphorus as the n type impuritiesare implanted in the N channel type MOS transistor of the high voltageinflicted area in order to alleviate the vertical electric field of anedge, n type semiconductor regions 259, 260, 261 and 262 and p typesemiconductor regions 263 and 264 are formed. Because of a difference ofdistribution coefficient, the n type semiconductor regions 259 and 260in the vicinity of the semiconductor surface are mainly constituted ofarsenic, and the n type semiconductor regions 261 and 262 implanteddeeper have a main component of phosphorus. Subsequently, as shown inFIG. 19A, the p type impurity (boron) and the n type impurity (As) areimplanted in the n type well region 213 forming the P channel type MOStransistor of the high voltage inflicted area HV, and thereby a p typesemiconductor region 266 forming the extension region, and asemiconductor region 267 which suppresses the punch through and has thesame conductivity type as the well and the concentration higher thanthat of the well region are formed. In the present embodiment, the masks(steps, ion implantation conditions) are changed with the high voltageinflicted area HV, the memory cell area MC and the peripheral circuitarea PERI. However, when a withstand pressure can satisfy the propertiesof a product, the P channel type MOS transistor can be formed with onemask (step) without changing the type and ion implantation condition(energy) of the impurity in the memory cell area MC, the peripheralcircuit area PERI and the high voltage inflicted area HV.

Additionally, the ion implantation order of the extension region and thesemiconductor region having the conductivity type opposite to that ofthe well and having the high concentration is not limited. That is, theion implantation of the region forming the P channel type MOS transistormay be performed before the ion implantation into the N channel type MOStransistor. Moreover, according to FIGS. 18B and 18C, in the N channeltype MOS transistor, the ion implantation is performed in order of thememory cell area, the peripheral circuit area and the high voltageinflicted area, but the order is not limited. To perform the ionimplantation of the high voltage inflicted area, depending on animpurity amount, the memory cell area and the peripheral circuit areaare not covered with the masks during the ion implantation, and it isalso possible not to prepare the mask for the high voltage inflictedarea. However, when there is a difference in the impurity amount,another mask needs to be prepared as shown in FIG. 18C.

As shown in FIG. 19A, after the silicon oxide layer is deposited on thesemiconductor substrate 200, for example, by a CVD process, the siliconoxide layer is etched having a selectivity for etching. Thereby, sidewall spacers (gate side wall layers) 265 are formed on side walls of thegate electrodes 230, 231, 232, 233, 234 and 235. Subsequently, as shownin FIG. 19B, photo resists 270 are used as masks, the p type impurity(boron) is ion-implanted in the n type wells 210 and 212, and p typesemiconductor regions 271 are formed on opposite sides of the gateelectrode 231, 232 and 235 on the n type well. The p type semiconductorregions 271 are formed in the gate electrodes 231, 232 and 235 and theside wall spacers 265 in a self aligned manner, and function as thesource/drain region of a p channel MISFET. Similarly, the photo resistis used as the mask to ion-implant the n type impurity (As) in the ptype wells 211 and 213, and n type semiconductor regions 280 which areto make a contact with the electrodes are formed. The n typesemiconductor regions 280 are formed with respect to the gate electrodes230, 233 and 234 and the side wall spacers 265 in the self alignedmanner. Moreover, the n type semiconductor regions 280 function as thesource/drain region of the n channel MISFET. As a result, thelow-concentration impurity semiconductor region is formed before theside wall spacers 265 are formed. After the side wall spacers 265 areformed, transistors having a lightly doped drain (LDD) structure to formthe high-concentration impurity semiconductor region are formed in therespective regions (FIG. 19C). Additionally, in the present invention,the source/drain region of the N channel type MOS transistor isprecedently formed, but the P channel type MOS transistor mayprecedently be formed.

Subsequently, as shown in FIG. 20A, the silicon oxide layer is etched,the surface of the source/drain semiconductor region is exposed, arefractory metal layer (Co, Ti, W, Mo, Ta) is deposited and annealed,the unreacted refractory metal layer is removed, and a part of thesurface of the semiconductor region forming the gate electrodes 230,231, 232, 233, 234 and 235 and the source/drain is subjected tosilicidation (290 and 291). Thereafter, a silicon nitride layer 292 isdeposited.

As shown in FIG. 19B, after the silicon oxide layer is deposited on thesemiconductor substrate 200 by the CVD or sputtering process, thesilicon oxide layer is polished, for example, by a CMP process, andthereby a first insulating layer between layers 300 having a flattedsurface is formed. Subsequently, the photolithography technique is usedto form a contact hole in the first insulating layer between layers 300.The contact hole is formed in a necessary portion on the n or p typesemiconductor region. A plug is formed in the contact hole, for example,as follows. First, a Titan nitride layer 301 is formed on the wholesurface of the semiconductor substrate 200 including the inside of thecontact hole. The Titan nitride layer can be formed, for example, by theCVD process. Since the CVD process is superior in a step coatingproperty, the Titan nitride layer having a uniform film thickness can beformed even in the fine contact hole. Subsequently, a metal (lithium)layer 302 to fill in the contact hole is formed. The metal layer can beformed, for example, by the CVD process. Subsequently, the metal layerand Titan nitride layer of the region other than the contact hole areremoved, for example, by the CMP process so that the plug can be formed.When such silicide layer is formed, contact resistance in the bottom ofa contact hole 12 can be reduced. Similarly, a contact hole is formed ina second insulating layer between layers 310. The contact hole is formedby a Titan nitride layer 311 and a metal (Tungsten) layer 312. Theseplugs are used in connecting a local wire. Subsequently, for example, aTitan nitride layer 321 and an aluminum layer 322 are formed on thewhole surface of the semiconductor substrate 200 by the CVD orsputtering process, the deposited layer is patterned by thephotolithography technique, and the wire of a first wire layer isformed. The first wire layer is used in a bit line and the like in amemory area. The insulating layer with which the wire is to be coated,such as a silicon oxide layer, is formed, the insulating layer isflatted by the CMP process, and a second insulating layer between layers330 is formed. A photo resist having an opening in a region in which thecontact hole is formed is formed on the second insulating layer betweenlayers 330, and the photo resist is used as the mask to etch the layer.Thereby, the contact hole is formed in the predetermined region of thesecond insulating layer between layers 330. The plug is formed in thecontact hole. The plug can be formed as follows. First, a barrier metallayer 340 is formed on the whole surface of the semiconductor substrate200 including the inside of the contact hole, and a metal (Tungsten)layer 341 to fill in the contact hole is further formed. Thereafter, themetal layer and barrier metal layer of the region other than the contacthole are removed by the CMP process to form the plug. The barrier metallayer has a function of preventing Tungsten from being diffused intoperipheries such as the second insulating layer between layers 330, andexamples thereof include the Titan nitride layer. Additionally, theexamples are not limited to the Titan nitride layer, and other metallayers may be used as long as the layer has the function of preventingTungsten from being diffused. For example, instead of Titan nitride,Tantalum (Ta) and Tantalum nitride (TaN) can also be used. Similarly asthe first wire layer, wire (351 and 352) of a second wire layer areformed. An insulating layer with which the wires are to be coated isformed, and flatted by the CMP process so that a third insulating layerbetween layers 360 is formed. Similarly as the second insulating layerbetween layers 330, the contact hole is formed in the third insulatinglayer between layers 360, and plugs (361 and 362) are formed in thecontact hole. Similarly as the second wire layer, wires (363 and 364) ofa third wire layer are formed. An insulating layer 370 with which thewires are coated is formed, and the silicon nitride layer is formed as apassivation layer 371 on the insulating layer. A probing process, resinmolding process and the like are performed before shipment of theproduct.

As a result of trial preparation of memory cells, in which arsenic isimplanted in the extension region and the region to make the contact andin which phosphorus is supplied in the extension region, using thepresent device structure, it has been seen that a standby current can bereduced by about 50% at 25° C. and 90° C. That is, the standby currentof the semiconductor device can be suppressed not only at a usualoperation temperature but also at a high temperature. When the presentstructure is employed, there is an effect that an operation guaranteetemperature (e.g., 70° C. or less) of the product can be set to be high.

When the present device structure is employed in a thin layer NMOS, thestandby current of the semiconductor device can be reduced to about 1.0μA from 2.5 μA in the conventional As structure. This effect is producedbecause the main component (about 70%) of the standby current is theGIDL current of NMOS.

Additionally, only phosphorus is used in the extension region of the Nchannel type MOS transistor of the memory cell area, but phosphorus andarsenic may sometimes be implanted for a high-speed operation. In thiscase, two types of ion sources are necessary, but there is an effectthat a driving current increases. The structure is similar to that ofthe N channel type MOS transistor of the high voltage inflicted area.Since it is necessary to perform the ion implantation with an energylower than that of the high voltage inflicted MOS, it is necessary tochange the mask for the ion implantation of the extension region of thehigh voltage inflicted area. As a result, the breadth of thesemiconductor region becomes narrower than that of the high voltageinflicted area.

Fourth Embodiment

FIG. 8 shows an embodiment in which the present invention is applied toa microprocessor. The circuit is formed on the semiconductor substratesuch as single crystal silicon using the semiconductor integratedcircuit manufacturing technique in which the insulating layer for use inthe gate of the MOS transistor has a thickness of 4 nm or less, and thetunnel leakage current is 10⁻¹² A/μm² or more at the power voltage of1.5 V.

A microprocessor 130 is constituted of an IP circuit 133, a cache memory131 and a CPU 132. Moreover, a control circuit 134 for controlling theactive and standby modes is also mounted on the microprocessor 130.

The ground source electrode line VSSM of the cache memory 131 isconnected to the potential VSSS higher than the ground potential via anN channel type MOS transistor MN200, and is also connected to the groundpotential VSS via an N channel type MOS transistor MN201. The gateelectrode of the N channel type MOS transistor MN200 is connected to acontrol signal STBY0. The gate electrode of the N channel type MOStransistor MN201 is connected to a control signal ACTV0.

The ground source electrode line VSSM of the CPU circuit 132 isconnected to the potential VSSS higher than the ground potential via anN channel type MOS transistor MN202, and is also connected to the groundpotential VSS via an N channel type MOS transistor MN203. The gateelectrode of the N channel type MOS transistor MN202 is connected to acontrol signal STBY1. The gate electrode of the N channel type MOStransistor MN203 is connected to a control signal ACTV1.

The ground source electrode line VSSM of the IP circuit 133 is connectedto the potential VSSS higher than the ground potential via an N channeltype MOS transistor MN204, and is also connected to the ground potentialVSS via an N channel type MOS transistor MN205. The gate electrode ofthe N channel type MOS transistor MN204 is connected to a control signalSTBY2. The gate electrode of the N channel type MOS transistor MN205 isconnected to a control signal ACTV2.

When the control signal STBY0 indicates “H”, and ACTV0 indicates “L”,the cache memory 131 is brought into the standby mode, and the potentialof VSSM becomes the voltage VSSS higher than the ground potential, forexample, 0.5 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and thereby the gate tunnel leakagecurrent is reduced. Additionally, the data in the cache memory isretained without being destroyed.

When the control signal STBY0 indicates “L”, and ACTV0 indicates “H”,the cache memory 131 is brought into the active mode, and the potentialof VSSM corresponds to the ground potential VSS. In this case, the gatetunnel leakage current of the MOS transistor increases as compared withthe standby mode.

When the control signal STBY1 indicates “H”, and ACTV1 indicates “L”,the CPU circuit 132 is brought into the standby mode, and the potentialof VSSM becomes the voltage VSSS higher than the ground potential, forexample, 0.5 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and thereby the gate tunnel leakagecurrent is reduced. Additionally, the data in a register file and latchis retained without being destroyed.

When the control signal STBY1 indicates “L”, and ACTV1 indicates “H”,the CPU circuit 132 is brought into the active mode, and the potentialof VSSM corresponds to the ground potential VSS. In this case, the gatetunnel leakage current of the MOS transistor increases as compared withthe standby mode.

When the control signal STBY2 indicates “H”, and ACTV2 indicates “L”,the IP circuit 133 is brought into the standby mode, and the potentialof VSSM becomes the voltage VSSS higher than the ground potential, forexample, 0.5 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and the gate tunnel leakage currentis reduced.

When the control signal STBY2 indicates “L”, and ACTV2 indicates “H”,the IP circuit 133 is brought into the active mode, and the potential ofVSSM corresponds to the ground potential VSS. In this case, the gatetunnel leakage current of the MOS transistor increases as compared withthe standby mode.

Fifth Embodiment

FIG. 9 shows an embodiment in which the present invention is applied tothe microprocessor. The circuit is formed on the semiconductor substratesuch as single crystal silicon using the semiconductor integratedcircuit manufacturing technique in which the insulating layer for use inthe gate of the MOS transistor has a thickness of 4 nm or less, and thetunnel leakage current is 10⁻¹² A/μm² or more at the power voltage of1.5 V.

A microprocessor 135 is constituted of an IP circuit 138, a cache memory136 and a CPU 137. Moreover, a control circuit 139 for controlling theactive and standby modes is also mounted on the microprocessor 135.

The power source electrode line VDDM of the cache memory 136 isconnected to the potential VDDD lower than the power voltage via a Pchannel type MOS transistor MP200, and is also connected to the powervoltage VDD via a P channel type MOS transistor MP201. The gateelectrode of the P channel type MOS transistor MP200 is connected to acontrol signal STBYB0. The gate electrode of the P channel type MOStransistor MP201 is connected to a control signal ACTVB0.

The power source electrode line VDDM of the CPU circuit 137 is connectedto the potential VDDD lower than the power voltage via a P channel typeMOS transistor MP202, and is also connected to the power voltage VDD viaa P channel type MOS transistor MP203. The gate electrode of the Pchannel type MOS transistor MP202 is connected to a control signalSTBYB1. The gate electrode of the P channel type MOS transistor MP203 isconnected to a control signal ACTVB1.

The power source electrode line VDDM of the IP circuit 138 is connectedto the potential VDDD lower than the power voltage via a P channel typeMOS transistor MP204, and is also connected to the power voltage VDD viaa P channel type MOS transistor MP205. The gate electrode of the Pchannel type MOS transistor MP204 is connected to a control signalSTBYB2. The gate electrode of the P channel type MOS transistor MP205 isconnected to a control signal ACTVB2.

When the control signal STBYB0 indicates “L”, and ACTVB0 indicates “H”,the cache memory 136 is brought into the standby mode, and the potentialof VDDM becomes the voltage VDDD lower than the power voltage, forexample, 1.0 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and thereby the gate tunnel leakagecurrent is reduced. Additionally, the data in the cache memory isretained without being destroyed.

When the control signal STBYB0 indicates “H”, and ACTVB0 indicates “L”,the cache memory 136 is brought into the active mode, and the potentialof VDDM corresponds to the ground potential VDD. In this case, the gatetunnel leakage current of the MOS transistor increases as compared withthe standby mode.

When the control signal STBYB1 indicates “L”, and ACTVB1 indicates “H”,the CPU circuit 137 is brought into the standby mode, and the potentialof VDDM becomes the voltage VDDD lower than the power voltage, forexample, 1.0 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and thereby the gate tunnel leakagecurrent is reduced. Additionally, the data in the register file andlatch are retained without being destroyed.

When the control signal STBYB1 indicates “H”, and ACTVB1 indicates “L”,the CPU circuit 137 is brought into the active mode, and the potentialof VDDM corresponds to the power voltage VDD. In this case, the gatetunnel leakage current of the MOS transistor increases as compared withthe standby mode.

When the control signal STBYB2 indicates “L”, and ACTVB2 indicates “H”,the IP circuit 138 is brought into the standby mode, and the potentialof VDDM becomes the voltage VDDD lower than the power voltage, forexample, 1.0 V. In this case, the voltage supplied between the gate andsource of the MOS transistor drops, and thereby the gate tunnel leakagecurrent is reduced.

When the control signal STBYB2 indicates “H”, and ACTVB2 indicates “L”,the IP circuit 138 is brought into the active mode, and the potential ofVDDM corresponds to the power voltage VDD. In this case, the gate tunnelleakage current of the MOS transistor increases as compared with thestandby mode.

Sixth Embodiment

FIG. 10 shows an embodiment in which the SRAM or the microprocessorusing the present invention is applied to a system operated by a batteryof a cellular phone or the like.

A battery 141, the SRAM described in the third embodiment and themicroprocessor 130 described in the fourth embodiment are mounted on acellular phone 140. A terminal for driving the battery, an SRAM and amicroprocessor are mounted on the single semiconductor substrate in thesemiconductor device. Moreover, a circuit 143 for generating the voltageVSSS higher than the ground potential, for example, 0.5 V from the powervoltage VDD is also mounted.

The SRAM 98 is brought into the standby mode at CS of “L”, a groundelectrode indicates 0.5 V, and thereby the gate tunnel leakage currentis reduced.

The microprocessor 130 is brought into the standby mode, when STBYindicates “H” and ACTV indicates “L”. The ground electrode indicates 0.5V, and thereby the gate tunnel leakage current is reduced. As a result,it is possible to lengthen a battery life.

Seventh Embodiment

FIG. 11 shows an embodiment in which the SRAM or the microprocessoraccording to the present invention is applied to the system operated bythe battery of a cellular phone or the like.

A battery 141, an SRAM 146 and a microprocessor 147 are mounted on acellular phone 144. A power supply chip 145 for supplying a power supplyVDDI of the SRAM 146 and the microprocessor 147 is also mounted.

FIG. 12 shows an operating waveform. In the active mode, a standbysignal STBY indicates “L”, and the power voltage VDD is supplied to theSRAM 146 and the microprocessor 147.

In the standby mode, the standby signal STBY indicates “H”, and thepotential lower than the power voltage VDD is supplied to the SRAM 146and the microprocessor 147. In this case, the gate tunnel leakagecurrent and the GIDL current are reduced. As a result, it is possible tolengthen the battery life.

Additionally, the present invention may be applied to a MIS transistorin which the gate oxide layer of the MOS transistor described above isused as the insulating layer.

According to the present invention, the leakage current can be reducedwithout destroying data.

It should be further understood by those skilled in the art that theforegoing description has been made on embodiments of the invention andthat various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

1. A method for manufacturing a semiconductor device including a pair ofN-channel type first and second MIS transistors, the method comprising:providing a pair of first and second P-type wells in which a first and asecond MIS transistor is to be formed, forming a gate isolation thinfilm and a gate electrode on each of the first and second P-type wellsimplanting phosphorus to the first P-type well, implanting arsenic tothe second P-type well, forming side walls for the gate electrode aftercompletion of implantation of phosphorus and arsenic, and implantingarsenic to each of the first and the second P-type wells aftercompletion of forming of the side walls.
 2. The method according toclaim 1, wherein: 2-1: the semiconductor device further comprises anSRAM memory cell and a control circuit for controlling the SRAM memorycell, 2-2: the first MIS transistor comprises an N-channel type MIStransistor within the SRAM memory cell, and 2-3: the second MIStransistor comprises an N-channel type MIS transistor within thecontrolling circuit.
 3. The method according to claim 2, wherein: 3-1:the semiconductor device further comprises an input/output circuitincluding a third MIS transistor, 3-2: a third P-type well is arrangedto be formed during forming of the first and the second P-type well,3-3: the gate isolation thin film and the gate electrode are configuredto be formed on the third P-type well, 3-4: arsenic is implanted intothe third P-type well after completion of forming of the side walls, and3-5: both phosphorus and arsenic are configured to be implanted into thethird P-type well before forming of the side walls.